1. Field of the Invention
The invention relates to an explosive charge which has a spatial shape comprising explosive material and which, in the course of the explosion, unfolds a spatially anisotropic pressure action in at least one main action direction, in which the pressure action is greater than in other directions.
2. Description of the Prior Art
A detonation of explosive generates, as a function of the quantity, configuration, and composition of the explosive, a strong pressure action in the environment of the location at which the detonation occurs. The pressure action is typically based on a chemical reaction of the explosive to form gaseous reaction products, the so-called vapors, which propagate at high velocities and at high temperature and density because of the large pressure differential to the environment. A propagating pressure wave is also generated in the surrounding air by the expanding vapors, which typically rushes ahead of the reaction products.
The occurrence of the pressure action may be illustrated on the example of the detonation of a spherical explosive, a so-called spherical charge. As a result of ignition of the spherical charge from the center and subsequent detonation, an air pressure wave and the vapors propagate uniformly in all spatial directions starting from the center of the detonation, that is, isotropically, the temperature of the reaction products, that is, the vapors, decreasing with increasing distance from the center. The pressure action of the vapors also decreases strongly with increasing distance from the location of the detonation.
FIGS. 2a and b show diagrams of two snapshots in regard to the pressure propagation during the explosion of a spherical charge. The diagrams each show the spatial pressure profile at the instant of the snapshot. Pressure values are plotted along the ordinates of the diagrams and distance values to the location of the explosion, scaled in charge radii of the spherical charge, are plotted along the abscissas. FIG. 2a shows the pressure action in the so-called near field, that is, in a distance range from the explosion location of only a few charge radii at an early instant, where a large contribution of the vapor flow to the pressure action is provided. The pressure value scaling in units of kilobars may be seen. The total pressure action in the distances of 1-2 charge radii discussed in FIG. 2a is caused very predominantly by the high flow pressure of the explosion vapors at the beginning of the vapor explosion.
Another image results at a later instant and thus at a greater distance from the starting point of the vapor expansion: with spherical explosive charges, one typically assumes that so-called far-field-type conditions exist from a distance of approximately 15 charge radii. The drop of the maximum pressure from the near field to the far field may be four orders of magnitude, that is, a factor of 10,000, or more. The pressure action in the so-called far field is shown for this purpose in FIG. 2b, in which the comparatively slight action of the air pressure wave dominates, it is noted that the scaling of the pressure values in bar, and the vapor flow hardly still contributes to the pressure action. The steep flanks recognizable in FIG. 2b at 9 charge radii distance characterize the front of the air pressure wave which runs ahead of the vapors. The air pressure wave is distinguished in particular by this discontinuity in the air pressure.
The pressure action thus drops very rapidly with distance for unshaped charges. If a range increase of the pressure action is desired, increasing the explosive quantity is not a suitable measure. To achieve the same maximum pressure at 10 times the distance, for example, an increase of the explosive mass by a factor of 1000 is necessary according to the scaling loss.
An array of possible implementations are known to increase the action at a predefined distance from the explosion location or to enlarge the action range without increasing the explosive quantity, in which, turning away from an isotropic action propagation, as in the spherical charge described above, the action is anisotropic. Some implementations of this type are outlined briefly hereafter:
So-called hollow charges provide sheathing of a rotationally-symmetric metal insert on one side with an explosive, which is capable upon detonation of collapsing the metal insert, which is usually implemented in the form of a thin-walled metal layer implemented as spherical or semi-spherical, longitudinally to the charge axis, which corresponds to the axis of symmetry of the metal insert. The metal insert is subsequently accelerated out of the hollow charge along the charge axis like a jet. The jet expands along the axis until finally particulation occurs. The optimum action of hollow charges, which are used in weapons for combating armored vehicles, for example, is therefore provided at short distances of a few charge diameters distance, so that a hollow charge is generally brought to the target as a warhead on a projectile and is triggered shortly before the target. A hollow charge of this type is explained, for example, in DE 31 17 091 C2, DE 33 36 516 A1, or DE 29 13 103 C2.
In an alteration of a hollow charge explained above, it is possible by extruding the cross-sectional profile of the hollow charge in a lateral dimension and by suitable material selection of the metal insert to generate a so-called linear charge, which generates a flat particle jet. See DE 37 39 683 C2, for example. Such explosive charges, which are typically referred to as cutting charges, are typically designed to cut through objects such as steel girders or armor at a short distance.
Reference is made in this context, for example, to DE 11 2005 000 960 T5, in which a single-phase tungsten alloy for a hollow charge insert is described, which has improved jet formation properties.
Furthermore, special forms of lined hollow charges are known, which are used in explosive shaped projectiles (see, for example, DE 39 41 245 A1) to form a coherent penetrator, which may fly ballistically over long distances and has a high penetrating power. Fundamentally, however, the action is like a jet or projectile for all known variants of hollow charges because of the metal insert typical for hollow charges.
Capsules which at least partially sheath the explosive quantity, made of metal, for example, are also known, which are broken into arbitrary or predefined fragments by the detonation. The energy released in the near field, that is, in the immediate surroundings of the explosive, is partially exploited to accelerate these fragments, for example, in the form of splinters, which subsequently propagate over relatively large distances, limited by the deceleration due to aerodynamic forces, and may thus cause a destructive action at a greater distance. In general, the range of the splinters and the spatial angle range covered thereby are greater than desired.
It has been possible to show on the basis of so-called cylindrical charges, in which the explosive assumes the spatial shape of a solid cylinder, in particular in combination with a suitable selection of the initiation points triggering the ignition on the explosive charge, that the pressure action may be increased or decreased in specific spatial directions. As shown by Schraml et al., “Effects of initiator position on near-field blast from cylindrical charges”, conference article on Military Aspects of Blast and Shock (MABS) 17, Las Vegas, Nev., USA (2002), for example, by the simultaneous ignition at the center points of the end surfaces of a cylindrical charge, an amplified pressure action may occur in the centerpoint plane perpendicular to the cylinder axis. In the best case, the propagation direction of the pressure action in the near field is limited to a two-dimensional disk in an idealized approximation. However, even with cylindrical charges it is to be assumed that from a relatively short distance, only far-field-type conditions still exist, in which the pressure action due to the vapors and/or the reaction products is slight, and it is solely dominated by the air pressure wave. The anisotropy of the pressure action in particular also decreases strongly with growing distance from the charge. See, for example: M. Held “Impulse Method for the Blast Contour of Cylindrical High Explosive Charges”, Propellants, Explosives, Pyrotechnics 24, 17-26 (1999) in this regard.
A further possibility for directed pressure increase is the use of solid dams which suppress the propagation of the explosion vapors in specific directions. However, this is connected with a significant growth of the total mass in a technical device, which is not acceptable for specific applications, in particular in cases in which the mass of the dam must be significantly greater than the explosive mass.